It has been found that the dyeability or mass coloration of synthetic polyamides preferably with anionic dyes can be improved by incorporating into untreated polyamide one or more of the following compounds:
a) a compound having at least one sterically hindered amino, imino or amido group (preferably amino); [hereinafter referred to as compounds a)]; or
b) a trimesic acid trialkylamide, or pyromellitic acid tetra-alkylamide, at least one alkyl group of which bears at least one free amino, imino, amido and/or alkylamino group [hereinafter referred to as compounds b)]; or
c) a trialkylamino, imino or amido substituted triazine, at least one alkyl group of which carries a free amino, imino, amido and/or alkylamino group [hereinafter referred to as compounds c)]; or
d) a dyestuff (preferably of the azo-, anthraquinone- or perinone series) that contains at least one group that is reactive to a hydroxy and/or amino group and is preferably free of sulphonic acid groups [hereinafter referred to as compounds d)]; or
e) a synthetic modified polyamide (preferably a polymeric or oligomeric isophthalic acid amide or terephthalic acid amide) containing at least one group that is reactive with a hydroxy and/or amino group [herein- referred to as compounds e)].
Compounds containing a sterically hindered amino group are preferably those containing a group of the formula 
in which
R is hydrogen, C1-8alkyl, C1-8alkoxy, or xe2x80x94COR5,
where R5 is hydrogen, C1-6alkyl, phenyl, COO(C1-4alkyl) or NR15R16;
where R15 is hydrogen, C1-12alkyl, C5-6cycloalkyl, phenyl or (C1-12alkyl)phenyl; and R16 is C1-12alkyl or hydrogen; or
R15 and R16 together with the N atom to which they are attached form a five- to seven-membered ring which may contain an additional N or O atom (preferably forming a piperidine or a morpholine ring).
Preferred groups containing sterically hindered amines are of the formula I to VI 
in which
R is hydrogen, C1-8alkyl, C1-8alkoxy, or xe2x80x94COR5;
where R5 is hydrogen, C1-6alkyl, phenyl, xe2x80x94COO(C1-4alkyl) or NR15R16;
where R15 is hydrogen, C1-12alkyl, C5-6cycloalkyl, phenyl or (C1-12alkyl)phenyl; and R16 is C1-12alkyl or hydrogen or
R15 and R16 together with the N atom to which they are attached form a five- to seven-membered ring which may contain an additional N or O atom (preferably forming a piperidine or a morpholine ring); and
Y is the group 
xe2x80x83where CO forms a part of the cyclic structure;
each R6 independently is selected from hydrogen, C1-2alkyl or phenyl, provided only one group R6 can be phenyl, or both groups R6 together form the group xe2x80x94(CH2)11xe2x80x94, xe2x80x94(CH2nxe2x80x94, xe2x80x94C(CH3)2xe2x80x94, xe2x80x94C(CH3)2xe2x80x94CH2CH2xe2x80x94 or xe2x80x94C(CH3)2CH2CH2CH(CH3)xe2x80x94, and
n is 1 or 2.
Compounds containing groups of formulae III, IV and V are known, for example, from U.S. Pat. No. 4,292,240 and Japanese Kokai 62-190786, the contents of which are are incorporated herein by reference.
More preferred compounds of a) to c) are those of formulae 1 to 38 below: 
in which each R3 independently is hydrogen or C1-12 alkyl;
R4 is a group of formula xcex1 or xcex2
xe2x80x83where Rxe2x80x2 is hydrogen, C1-6 alkyl, C1-4 alkoxy or xe2x80x94COxe2x80x94C1-14 alkyl.
A is C2-3 alkylene;
R4xe2x80x2 is of formula xcex1xe2x80x2 or xcex1xe2x80x3
R2 is C1-3 alkyl. 
xe2x80x83where 
Preferred groups that are reactive to xe2x80x94OH or xe2x80x94NH2 (of compounds of d) and/or e) are e.g. those known as reactive groups in the chemistry of reactive dyes. More preferably such are cyclic groups having at least 2 nitrogen atoms (separated preferably by one or two carbon atoms), e.g. triazinyl-, pyrimidyl-, quinoxalyl-, quinazolyl groups phthalazinyl, benzoxazolyl and benzthiazolyl groups, bearing 1 to 3 chlorine atoms on the carbon atoms adjacent to the nitrogen atoms.
Additional more preferred reactive groups are of formula i) to xi) 
xe2x80x94COxe2x80x94CH2 CH2 SO2xe2x80x94C6H5xe2x80x83xe2x80x83vii)
xe2x80x94COxe2x80x94CH=CH2xe2x80x83xe2x80x83viii)

xe2x80x94COxe2x80x94CHxe2x95x90CCl2xe2x80x83xe2x80x83x)
xe2x80x94COxe2x80x94CH2xe2x80x94Z andxe2x80x83xe2x80x83xi)

in which Z is a halogen (preferably chlorine) or a group of the formula 
where Axe2x88x92 is an anion.
Preferably Alkyl is C1-4alkyl.
Such groups are described in The Chemistry of Synthetic Dyes, Vol. VI, Chapter Ixe2x80x94by E. Siegel, [editor K. Venkataraman,]Academic Press. (1972);
Chimica, Supplement Mxc3xa4rz 1968, Farben Symposium Interlaken, p. 102 et seqxe2x80x94E. Siegel xe2x80x9cChemie der Reactivfarbstoffexe2x80x9d and
Angew. Chem. 76, (1964), No. 10, p. 423 et seqxe2x80x94K. G. Kleb xe2x80x9cUeber neue Reactivfarbstoffexe2x80x9d.
Of particular interest are those compounds a) to c) for incorporation into synthetic polyamides having one or two sterically hindered amino groups and one or two groups reactive to xe2x80x94OH and/or xe2x80x94NH2.
Such compounds having one or two sterically hindered amino groups and one or two groups reactive to OH and/or xe2x80x94NH2 are of formulae 39 to 46 below: 
R4xe2x80x94COxe2x80x94CHxe2x95x90CH2xe2x80x83xe2x80x8341.
R4xe2x80x94COxe2x80x94CH2CH2SO2C6H5 xe2x80x83xe2x80x8342.
R4xe2x80x94SO2xe2x80x94CHxe2x95x90CH2xe2x80x83xe2x80x8343.

Compounds of formulae 39-46 can be prepared conventionally, e.g. by condensing the appropriate acid chloride or the cyanuric-acid chloride with a free amino or imino group of a sterically hindered amine containing compound in appropriate amounts.
The preferred azo, anthraquinone or perinone dyestuffs of compounds d having groups that are reactive to hydroxy and/or amino groups are preferably those described in Examples 50 to 69 inclusive, hereinafter described.
Examples 50-58 are in 2:1 chromium complex form.




















The preferred polymeric isophthalic or terephthalic acid amides of compounds e) and a) respectively are those of formula VII and VIII
Paxe2x80x94(R11)nxe2x80x83xe2x80x83VII
Paxe2x80x94(COxe2x80x94R12)nxe2x80x83xe2x80x83VIII
in which Pa is a nitrogen containing radical of a synthetic polyamide,
R11 is a group attached to the nitrogen atom of the polyamide molecule containing one or more groups reactive to hydroxy and/or amino,
R12 is a group containing a sterically hindered amino group and
m is 1 or 2.
The compounds of formulae VII and VIII can be added to a synthetic polyamide before, during or after the polycondensation synthesis or worked into the molten mass.
The compounds of formula VIII can be produced when a synthetic polyamide having a terminal carboxy group or functional derivative thereof (e.g. the acid chloride or an ester) is reacted during the polycondensation process with one or more amino groups or one or more sterically hindered amino group containing compounds, preferably of aromatic nature. The reactive groups are preferably those described above as groups of formula i-xii.
The compounds of the formula R12H which are used for producing the compounds of formula VIII have a reactive nitrogen atom that is either an amino group or part of a cycle group, for example a piperazine group. These compounds may also contain one or two sterically hindered nitrogen atoms in a cyclic structure, for example Nxe2x80x94C1-4alkyl or N-acyl substituted 2,2,6,6-tetraalkylpiperidyl-4-groups.
The synthetic polyamides according to the invention can be dyed in the mass with any type of dyestuff, provided that it is stable at high temperatures (of the melt). Preferred dyestuff groups are the monoazo-metal complexes, in particular the chrome complexes that are sufficiently stable at high temperatures to be used. Preferred reactive dyestuffs that can be used are the halogen-containing triazinyl or vinyl group containing metallized azo dyestuffs (i.e., those metallized with chromium, nickel or copper). Such reactive dyestuffs have been commercially available for a number of years.
The preparation of modified synthetic polyamides according to the invention can be effected in a conventional manner, preferably by mixing the reactive compounds with molten synthetic polyamide, e.g. in an extruder prior to spinning, or before or during the polycondensation process of the synthetic amide itself.
Generally one uses 0.5 to 5 percent by weight of the compounds a) to e) based on the weight of synthetic polyamides. More preferably 1 to 2 percent by weight of the compounds a) to e) are used.
The synthetic polyamides according to the invention (e.g. containing a compound a) to e)) are outstanding in many respects compared to synthetic polyamide which does not contain a compound a) to e)xe2x80x94hereafter referred to as xe2x80x9cuntreated polyamidexe2x80x9d. When dyeing untreated polyamide and polyamide according to the invention with acid dyes is carried out (using the same quantity of dyestuffs on the substrate), a considerably deeper and more brilliant dyeing is obtained with the synthetic polyamides according to the invention than untreated polyamide. Bath exhaustion is noticeably better and the fastnesses, especially wet fastnesses, are improved.
If reactive dyes are used to dye synthetic polyamides according to the invention, in general between 0.05 and 5 percent by weight of the reactive dyes are used based on the weight of synthetic polyamides. More preferably the amounts of reactive dye used is between 0.1 and 3 percent by weight. The dyeings so obtained are also deeper than exhaust dyeings made with the same amound of dye on the untreated synthetic polyamide.
Further according to the invention, there is provided a process for aftertreating a synthetic substrate, for example polyamide, cellulose and cellulose derivative substrates that have been dyed with anionic dyes characterized in that a solution or dispersion of a compound a) (preferably cycloaliphalic compound containing at least one sterically hindered amine group) is applied thereto.
Preferably the sterically hindered group is a 2,2,6,6-tetramethyl-piperidinyl group.
Preferably the substrate is polyamide.
A preferred compound a) is one containing the groups I to VI as defined above.
The compound a) containing groups of formula I are more preferred.
Most preferred compounds a) are of formula XX and XXI 
in which R40 is a group of the formula 
where Ra is hydrogen, methyl or xe2x80x94COxe2x80x94CH3.
R50 is chloro or a significance of R40 independent of R40 
na is 2, 3 or 4.
Preferred compounds a) are also those of formula 1 to 38 that contain two or three sterically hindered amine groups.
Preferred dyes that can be used to dye polyamide prior to aftertreating with compounds a) are selected from:
C.I. Acid Blue 25,40,72,106,126,129,227,230,278,280 and 296
C.I. Acid Yellow 59,112,114,127 and 129
C.I. Acid Red 261 and 404
C.I. Acid Green 40
C.I. Acid Orange 82
C.I. Acid Violet 66
C.I. Acid Brown 28,30 and 289
C.I. Acid Black 58 and 115
C.I. Solvent Yellow 83
C.I. Solvent Red 90:1,91 and 92
C.I. Solvent Black 45